Photoluminescence and photoluminescence excitation spectroscopies are utilized to study excitons in GaAs/AlGaAs quantum wells (QWâ€™s) fabricated by molecular beam epitaxy on a GaAs buffer layer grown on a Si substrate. The buffer layer was grown by metalorganic vapor phase epitaxy. The experimental results are understood in terms of a uniform biaxial tension of approximately 3 kbar present in the plane of growth for both the QWâ€™s and the GaAs buffer. An important consequence of the biaxial tension is that for QWâ€™s with well widths larger than â‰Š15 nm the light-hole and heavy-hole subbands cross each other in energy, resulting in a light-hole exciton energy lower than that of the heavy-hole exciton, opposite to the case of QWâ€™s grown on GaAs substrates.

We have directly observed spin relaxation of excitons in the picosecond region using time-resolved polarization absorption measurements. With the help of spin-dependent optical nonlinearity of excitonic absorption, we obtained a fast decay of spin-up carriers and a fast accumulation of spin-down...

A study is reported of exciton luminescence in GaAs double quantum wells produced in electric and magnetic fields. It has been found that the indirect-exciton line (IX) behaves anomalously, namely, one observes a magnetic-field-induced low-energy shift of the IX line, and the onset of periodic...

The binding energy of an exciton in the GaAs/AlAs quantum well is discussed including the influence of interface optical phonons and bulk longitudinal optical phonons confined in the well under hydrostatic pressure. The dependence of the phonon energies on pressure is considered using a linear...

The changes in binding energy and oscillator strength of the exciton state due to the screening by a quasi-two-dimensional electron gas are calculated self-consistently in the approximation of noninteracting electrons and in the local field approximation. It is shown that the collapse of the...

A novel method for determining the local concentration of Al in the AlxGa1-xAs layer of AlxGa1-xAs-GaAs multiple quantum well structures is reported. By scanning a 10 Ã… electron beam across the interface, the (200) dark-field scanning transmission electron microscopy (STEM) image shows the...

We monitor the near-infrared (NIR) transmission of a GaAs/AlGaAs multi quantum well while illuminated with intense terahertz (THz) pulses. We present the first clear evidence of the intra-excitonic Autler-Townes effect when pumping the 1s-2p transition of the heavy-hole exciton. We discuss our...

Two types of excitons, localized at opposite interfaces and characterized by different magnitudes of the exchange interactions at the same radiation energies, are simultaneously in type-II GaAs/AlAs superlattices. It is shown that the additional long-wavelength luminescence line in superlattices...

Optical reflection spectra from a Ga[sub 0.7]Al[sub 0.3]As/GaAs heteroboundary are calculated using the approximation of a strongly localized exciton wave function. The calculation is based on electron Î“[sub 6] and hole Î“[sub 8] kp-Hamiltonians with position-dependent parameters.